The invention relates to a self-sealing washer comprising a spacer ring and a sealing ring formed thereon.
A washer of a similar type has been described in the art. This washer of a known design is intended for sealing and simultaneous support of machine parts which are pressed against each other vertically, for instance, of the plane surfaces between the head of a machine screw and the machine part supported thereby. For several reasons, however, the use properties are not satisfactory.
This washer is made of a spacer ring with a rectangular profile, to which is vulcanized on the inside or outside circumference relative to the direction of pressure application, a sealing ring. The effectiveness, therefore, does not include sealing for pressures alternating in direction, which is a disadvantage.
The contact pressures of the sealing ring against the plane surfaces of the sealed machine parts result from the elastic pretensioning force generated by the deformation and the reaction forces of the sealed-off medium superimposed thereto. Thus, it does not provide constant sealing under changing pressures and can be impaired by fatigue of the elastomer material of the sealing ring.
Difficulties can arise during the installation if, during compression, the sealed surfaces are moved not only vertically but also transversely which occurs when using screws. Then, special, costly measures must be taken to prevent friction damage or destruction of the sealing ring. These measures include, for instance, providing a high finish of the plane surfaces and providing a centering hole for supporting the outside circumference. Also, repeated use of such washers after they are disassembled is not possible.